Regulatory T cells (Tregs) have been recognized as an important subset of T cells, and modulation of Tregs has been used in transplantation tolerance induction, autoimmune disease treatment, and cancer treatment. Antigen-specific immune responses such as those targeted against tumors are suppressed by Tregs characterized by CD4+CD25highFoxP3+ expression. CD25+Treg depletion combined with tumor vaccination is a potentially promising approach to improve cancer treatment.